The overall goal of this project is the discovery and development of new anticancer agents with solid tumor selectivity from leads obtained from marine cyanobacteria. The need for new anticancer drugs is significant given the paucity of agents active against the major solid tumors of man. An underlying hypothesis of our screening strategy is that it will generate drugs active against the major solid tumors (such as lung and colon), which are not effectively treated at present. Marine cyanobacteria are abundant as both free-living and symbiotic tropical organisms, and have a correspondingly rich and diverse secondary metabolism. We propose to produce between 1000 and 1500 extracts per year from field collected and cultured tropical marine microalgae, mainly cyanobacteria, with a focus on those of low natural biomass or found in symbiosis with marine invertebrates, such as sponges and tunicates and to characterize "super-producing" marine cyanobacterial strains. Extracts will also be obtained from collections of tuft-forming marine cyanobacteria and planktonic/thin slime forming marine cyanobacteria for culture as well as cultured cyanobacteria isolated from invertebrate hosts under natural product-eliciting conditions. We will use a unique in vitro disk diffusion assay to both identify solid tumor selectivity in the extracts and to direct the isolation of putative anticancer agent. Drug structure will be determined by using and developing innovative NMR pulse sequences and integrating this with MS and other spectroscopic information. If necessary; we will scale-up the culture or recollect selective species to provide sufficient drug to advance to preclinical studies. The first step requires about 20 mg of drug and incorporates information from in vitro concentration-survival clonogenic studies on a solid tumor with pharmacokinetic information (serum and tumor drug levels). The drug is first formulated for intravenous administration and an HPLC assay is developed to monitor serum and tissue levels. The clonogenic/pharmacokinetic information is analyzed to determine whether the more expensive in vivo therapeutic trial should be undertaken. If positive, then an efficacy trial in tumor-bearing mice will be carried out in at least one xenograft model. Therapeutically active drugs will be pursued outside of this application.